Capacitive sensors are largely used as contact or pressure sensors. According to a particular embodiment, they may comprise an array of capacitors ordered in rows and columns connected through row and column lines (or plates), as schematically depicted in FIG. 1. These sensors produce a distribution map of the pressure even on a relatively large surface. The capacitance of each single capacitor of these sensors depends on the degree of deformation undergone by the dielectric layer of the capacitor, induced by a compressive force exerted thereon. By reading the values of the capacitances of all the capacitors of the array, an “array” of values (“frame”) describing the spatial distribution of the pressure field on the sensing surface of the sensor is obtained.
The pressure field on the sensing surface may be easily displayed by a gray scale image, in which the luminance of each pixel is a function of the measured capacitance of a corresponding capacitor of the array.
Several problems have so far prevented realization of relatively low cost systems for reading such capacitive pressure sensors with good precision and with a great flexibility of use such to make them usable in particularly demanding applications. The precision of the sensing (reading) system of these sensors is negatively affected by the fact that the reading of the capacitance of a capacitor of the array is disturbed by the presence of the other capacitors and by parasitic capacitances between adjacent rows and columns. The capacitances affecting the reading of a single capacitor may add up to be 2 or 3 orders of magnitude greater than the capacitance of the selected capacitor being read to be detected. Moreover, a truly multipurpose system suitable to be used in many types of applications should work properly even if it is necessary to vary from time to time the number of addressable rows and columns of the array, depending on the particular application.